Guru3D - Driver Sweeper
Instructions from page:
Use the official uninstaller(s) of the driver(s) you want to uninstall.
Reboot your PC in Safe Mode.
Run Driver Sweeper and select what to clean.
Analyse lists all the entries possible to remove, cleaning removes the entries selected.
More drivers can be selected for the same cleaning process.
After that, shut your system down, remove old GPU, install new GPU, boot system up, install new drivers. Would be a good idea to download the latest drivers for the card beforehand, since they're usually a decent sized installer. That way you don't have to wait for the download in a limited resolution or anything like that.